1. Field of the Invention
This invention is directed to: systems and methods for dewatering materials; to concrete treatment and reclamation; reclamation of components of solidified concrete and of slurries thereof; treatment of components of such mixtures; and disposal thereof.
2. Description of Related Art
The surface of concrete roadways often deteriorates and degrades so that the surface, which was relatively smooth when the roadway was made, becomes uneven and rough. Such uneven rough surfaces can be smoothed out by removing a top portion of the roadway. In certain prior art systems grinding apparatus grinds away a top portion of such a concrete roadway. Ground off concrete is removed in a fluid slurry as the grinding operation proceeds.
In the past, the fluid slurry has been dumped on the side of a roadway or transported from the site of the roadway to an earthen pit or landfill. Today this is not feasible due to, among other things, the high pH of the material which renders it hazardous. In certain prior art methods in which the material is treated off site, a typical price for the treatment and disposal of one truckload is about $38,000.
Often solidified concrete is ground up to produce concrete grindings from which concrete solids are reclaimed. Typically an average cubic yard of concrete weighs about 3500 pounds, of which about 1500 pounds is coarse aggregate (e.g. rock between +4 sieve size or mesh and xe2x88x922 inches, i.e. the pieces have a largest dimension of 2 inches and the pieces with a smallest dimension are captured on a 4 mesh screen) contains about 1500 pounds of fine aggregate (e.g. rock and sand between +200 mesh and xe2x88x924 mesh); about 300 pounds of water; injected air and soaps as desired; binders; cement; fly ash; fiber; and various chemicals. Aggregate particle size ranges include boulders, cobbles, coarse aggregate, fine aggregate, and mineral filler, which are defined in terms of particle size as follows:
Boulders and cobbles are found in naturally occurring deposits. They can be crushed and sized to produce coarse and fine aggregate. Mineral filler is a flour-size material that is produced from aggregate crushing and processing.
Aggregate is used as a component of portland cement concrete (PCC), asphalt concrete, or in other construction materials. Aggregate represents 70 to 85% by weight (60 to 75% by volume) of PCC and 90 to 95% by weight (75 to 85% by volume) of asphalt concrete mixtures. The workability, strength, durability, moisture susceptibility, and performance of these construction materials are influenced greatly by the aggregate characteristics.
There is a need for a concrete treatment that is efficient for the reclamation, treatment and proper disposal of cement solids and other materials. There has long been a need for such a system which efficiently produces re-usable cement solids.
The present invention, in certain aspects, discloses a system for handling a fluid slurry containing water and concrete ground from a roadway. The system according to the present invention can be provided on-site where the roadway grinding operation occurs or at a site remote from the location of the grinding operation. When the system according to the present invention is present on-site, system components are mounted on appropriate skids and/or trailers. In one such aspect the entire system is mobile. When the system according to the present invention is located at a site remote from the grinding operation, typical ground emplacement of system components is utilized.
In certain aspects such a system produces three products from concrete grindings (or three waste streams): 1.) sand (i.e., all particles passing through a screen of known mesh, e.g., but not limited to 200 mesh; 2.) cement paste (fine particles of cement and fine ground particles, e.g. of rock, from a grinding process; and 3.) water. In certain embodiments all (100%) slurry components are reclaimed and can be re-used.
In certain embodiments a system for handling and treating a fluid slurry with water and ground-up concrete includes a vibratory separator to which the slurry is fed. The vibratory separator has one or more screens or screen assemblies which screen solids from the slurry and produce a stream of water with some solid slurry components still remaining therein.
Solids screened out by the screen(s) flow from the vibratory separator for collection and/or disposal. The stream with water and some solid slurry components is then fed to a decanting centrifuge (either on-site with the vibratory separator or remote therefrom) which further separates the water from the remaining solid components. Clean water produced by the centrifuge is collected and stored; fed to other points in the system; and/or returned to the grinding operation. Optionally this clean water is filtered for further purification. Optionally, a flocculant is added to the stream coming from the vibratory separator prior to its introduction to the centrifuge to facilitate centrifugation of the fluid.
In embodiments in which the slurry is transported in trucks from the grinding location, a pump apparatus pumps the slurry from the trucks to the vibratory separator. Optionally, an air or an air/water sparge may be used within the trucks to facilitate removal of the slurry therefrom.
Fluid flowing from the vibratory separator is, in one aspect, collected in a tank which has one, two, three, four, or more agitators to maintain fluid homogeneity prior to fluid feed to the centrifuge.
The present invention, in certain embodiments, discloses and teaches a system and method for treating concrete grindings to reclaim constituents thereof, and, in one aspect, for preparing certain of the constituents for either re-use or safe disposal. Concrete grindings are produced from large pieces of concrete ground up in a grinding unit. A portable grinding unit may be used.
In certain methods according to the present invention a slurry is formed in the grinding unit that includes concrete, cement solids, and water. The slurry is then pumped to a vibratory separator to separate sand in the grindings from the slurry of material. In one particular aspect the vibratory separator is a shale shaker with fine mesh screens.
The resulting fluid stream with some components removed (in certain aspects, at least 90% of the sand is removed is then fed to one, two, or more centrifuges (e.g. decanting centrifuges) to separate cement solids in the fluid stream from the water in the fluid stream. The fluid stream may contain traces of silt or soil from the concrete""s surface which are also removed in the system according to the present invention.
The water from the centrifuge(s) may be cleaned and treated with a polymer. The pH of the resulting clean water is, if needed, adjusted so that the clean water is pH neutral. This may be accomplished by adding chemicals, e.g. acid, e.g. muriatic acid, hydrochloric acid or phosphoric acid to the clean water. Optionally the cleaned pH adjusted water may be filtered to remove undesirable material, e.g. sediment or colloidal size solids. The resulting water may then be disposed of or used again in the system (e.g. returned to a container, tank, and or truck; e.g., for re-use in the grinding operation).
Sand and other components produced by the vibratory separator may be collected for re-use or disposal in suitable bins or receptacles. Cement solids, typically in the form of a paste, flowing from the centrifuge(s) may also be collected in suitable bins or receptacles.
It is, therefore, an object of at least certain preferred embodiments of the present invention to provide:
New, useful, unique, efficient, nonobvious systems and methods for handling and treating a slurry with water and concrete grindings to reclaim constituents thereof for re-use and/or safe disposal;
Such systems that use one or more vibratory separators and/or one or more decanting centrifuges; and
Such systems that produce safely disposable cleaned and/or reusable water and/or reusable cement solids.
Certain embodiments of this invention are not limited to any particular individual feature disclosed here, but include combinations of them distinguished from the prior art in their structures and functions. Features of the invention have been broadly described so that the detailed descriptions that follow may be better understood, and in order that the contributions of this invention to the arts may be better appreciated. There are, of course, additional aspects of the invention described below and which may be included in the subject matter of the claims to this invention. Those skilled in the art who have the benefit of this invention, its teachings, and suggestions will appreciate that the conceptions of this disclosure may be used as a creative basis for designing other structures, methods and systems for carrying out and practicing the present invention. The claims of this invention are to be read to include any legally equivalent devices or methods which do not depart from the spirit and scope of the present invention.
The present invention recognizes and addresses the previously-mentioned problems and long-felt needs and provides a solution to those problems and a satisfactory meeting of those needs in its various possible embodiments and equivalents thereof. To one skilled in this art who has the benefits of this invention""s realizations, teachings, disclosures, and suggestions, other purposes and advantages will be appreciated from the following description of preferred embodiments, given for the purpose of disclosure, when taken in conjunction with the accompanying drawings. The detail in these descriptions is not intended to thwart this patent""s object to claim this invention no matter how others may later disguise it by variations in form or additions of further improvements.